Hello Peter:
The description of two DFS 230's being
left behind at Bordeaux is consistent with them being intended for transport to Japan via U boat - transport U Boats used Bordeaux as a base for departure for Japan.
This link provides some information about the fascinating story of the Far East U Boats:
http://www.uboataces.com/articles-fareast-boats1.shtml
One thing you will note is the very heavy losses of these boats. Even if any DFS 230 was ever sent, it is very likely to have been lost
en route.
To take your research forward, you could try to find the cargo lists for all the transport U Boats dispatched to the Far East. This would be one for the U Boat community.
Regards
Don W